The subject matter of the present disclosure broadly relates to the art of document imaging systems and, more particularly, to a document imaging system that is capable of reducing variations in the recorded image of an original document, such as may be used in connection with an electronic document storage system or in association with a printing system, for example, as well as a method of imaging original documents using the same.
Document imaging systems of a wide variety of types and kinds are known and commonly used. For example, such systems often take the form of automatic document handlers or scanners for electrophotographic copy machines and other printing systems. In general, known document imaging systems optically transmit a reflected image of an original document to an image recording device, such as an electrophotographic marking engine or a digital imaging sensor, for example. While other performance-related factors may also be considered, such as imaging rate (i.e., images per minute) and image resolution, for example, it is generally desirable for the recorded image to match the original document as closely as is reasonably possible.
Notwithstanding the common usage and overall success of known document imaging systems, some areas remain in which improvements in performance and/or operation of document imaging systems can be attained. For example, the image of an original document that is recorded by known document imaging systems can include variations of certain types and/or kinds when compared with the original document. The type, kind and occurrence rate of such variations differ from imaging system-to-imaging system. For example, the occurrence of lateral image offsets as well as changes in contrast from that of the original document have been observed in some document imaging systems, such as those that operate at relatively low imaging rates, for example.
FIG. 5 illustrates one example of a conventional document imaging system 50 during the use of which one or more of the aforementioned image variations have been observed to occur. Document imaging system 50 includes a transparent imaging platen 52 and an image recording device 54 that is in optical communication with the imaging platen by way of an imaging pathway 56. A document transport system (not numbered) includes a document transport roll 58 that is supported for rotation about an axis AX. A document entry guide 60 is supported adjacent the document transport roll such that a document entry pathway 62 is formed between the document guide and the document transport roll. First and second document exit guides 64 and 66 at least partially define a document exit pathway 68. Typically, first document exit guide 64 will be fixed on or along the imaging platen and second document exit guide 66 will be moveable relative to the imaging platen.
The document entry guide is supported on the same side of imaging platen 52 as the document transport roll and includes a guide surface 70 that has a distal end 72 spaced a distance from the imaging platen. The document transport roll is adapted to transport an original document from a first position DOC1 that is generally upstream of imaging pathway 56 to a second position DOC2 that is generally downstream of the imaging pathway.
As the original document is transported from the first position toward the second position, the trailing edge TEG of the original document will be supported on of along guide surface 70 until the point at which the trailing edge reaches distal end 72 of the document guide. As the original document is transported further downstream, the trailing edge becomes unsupported and falls or is otherwise displaced toward imaging platen 52. This occurrence is sometimes referred to in the art as an “edge flick” and can result in lateral image offsets due to the sudden movement of the portion of the original document that is being imaged at the time the trailing edge becomes unsupported by the document guide.
Another image variation that may occur under such conditions of operation is a change in contrast (i.e., the lightness/darkness level) from one portion of the recorded image to another. This image variation has been recognized as having a relation to the trailing edge of the original document becoming unsupported by the document guide. In particular, it has been recognized that the trailing edge of the original document becomes supported on the imaging platen once disengaged from the document guide. This results in a change in the angle and/or other aspects of illumination of the light emitted by exposure lamps 74 and the reflection of the light from the original document along imaging pathway 56, which are sometimes referred to in the art as “integrated cavity effects.”
Accordingly, it is believed desirable to develop a document imaging system as well as a printing system and method of imaging that at least partially addresses the foregoing and/or other issues.